diff --git a/app/authentication/auth.py b/app/authentication/auth.py
index 841222279..357151fba 100644
--- a/app/authentication/auth.py
+++ b/app/authentication/auth.py
@@ -3,7 +3,7 @@ from sqlalchemy.exc import DataError
 from sqlalchemy.orm.exc import NoResultFound
 
 from notifications_python_client.authentication import decode_jwt_token, get_token_issuer
-from notifications_python_client.errors import TokenDecodeError, TokenExpiredError
+from notifications_python_client.errors import TokenDecodeError, TokenExpiredError, TokenIssuerError
 
 from app.dao.api_key_dao import get_model_api_keys
 from app.dao.services_dao import dao_fetch_service_by_id
@@ -39,8 +39,10 @@ def requires_auth():
     auth_token = get_auth_token(request)
     try:
         client = get_token_issuer(auth_token)
-    except TokenDecodeError:
-        raise AuthError("Invalid token: signature", 403)
+    except TokenDecodeError as e:
+        raise AuthError(e.message, 403)
+    except TokenIssuerError:
+        raise AuthError("Invalid token: iss not provided", 403)
 
     if client == current_app.config.get('ADMIN_CLIENT_USER_NAME'):
         return handle_admin_key(auth_token, current_app.config.get('ADMIN_CLIENT_SECRET'))
@@ -76,8 +78,8 @@ def handle_admin_key(auth_token, secret):
     try:
         get_decode_errors(auth_token, secret)
         return
-    except TokenDecodeError:
-        raise AuthError("Invalid token: signature", 403)
+    except TokenDecodeError as e:
+        raise AuthError(e.message, 403)
 
 
 def get_decode_errors(auth_token, unsigned_secret):
diff --git a/requirements.txt b/requirements.txt
index a71037824..594f12317 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -19,7 +19,7 @@ monotonic==1.2
 statsd==3.2.1
 jsonschema==2.5.1
 
-git+https://github.com/alphagov/notifications-python-client.git@1.3.0#egg=notifications-python-client==1.3.0
+git+https://github.com/alphagov/notifications-python-client.git@2.0.0#egg=notifications-python-client==2.0.0
 
 git+https://github.com/alphagov/notifications-utils.git@9.1.1#egg=notifications-utils==9.1.1
 
diff --git a/tests/app/authentication/test_authentication.py b/tests/app/authentication/test_authentication.py
index 3a6d5b4d2..be7217b07 100644
--- a/tests/app/authentication/test_authentication.py
+++ b/tests/app/authentication/test_authentication.py
@@ -1,3 +1,6 @@
+import jwt
+import uuid
+import time
 from datetime import datetime
 
 import pytest
@@ -41,6 +44,46 @@ def test_should_not_allow_request_with_incorrect_token(notify_api, sample_user):
             assert data['message'] == {"token": ['Invalid token: signature']}
 
 
+def test_should_not_allow_request_with_no_iss(client):
+    # code copied from notifications_python_client.authentication.py::create_jwt_token
+    headers = {
+        "typ": 'JWT',
+        "alg": 'HS256'
+    }
+
+    claims = {
+        # 'iss': not provided
+        'iat': int(time.time())
+    }
+
+    token = jwt.encode(payload=claims, key=str(uuid.uuid4()), headers=headers).decode()
+
+    response = client.get('/service', headers={'Authorization': 'Bearer {}'.format(token)})
+    assert response.status_code == 403
+    data = json.loads(response.get_data())
+    assert data['message'] == {"token": ['Invalid token: iss field not provided']}
+
+
+def test_should_not_allow_request_with_no_iat(client, sample_api_key):
+    # code copied from notifications_python_client.authentication.py::create_jwt_token
+    headers = {
+        "typ": 'JWT',
+        "alg": 'HS256'
+    }
+
+    claims = {
+        'iss': str(sample_api_key.service_id)
+        # 'iat': not provided
+    }
+
+    token = jwt.encode(payload=claims, key=str(uuid.uuid4()), headers=headers).decode()
+
+    response = client.get('/service', headers={'Authorization': 'Bearer {}'.format(token)})
+    assert response.status_code == 403
+    data = json.loads(response.get_data())
+    assert data['message'] == {"token": ['Invalid token: signature, api token is not valid']}
+
+
 def test_should_not_allow_invalid_secret(notify_api, sample_api_key):
     with notify_api.test_request_context():
         with notify_api.test_client() as client: